Sensor apparatus

ABSTRACT

A sensor apparatus includes: an element substrate; a detecting section disposed on an upper surface of the element substrate, the detecting section including a reaction section having an immobilization film to detect an analyte; a first IDT electrode configured to generate an acoustic wave which propagates toward the reaction section, and a second IDT electrode configured to receive the acoustic wave which has passed through the reaction section; and a protective film located on the upper surface of the element substrate so as to cover the first IDT electrode, the second IDT electrode, and at least part of the immobilization film, the protective film extending between and contacting with the immobilization film and at least one of the first IDT electrode and the second IDT electrode.

TECHNICAL FIELD

The present invention relates to a sensor apparatus which is capable ofmeasurement on the properties or constituents of an analyte liquid.

BACKGROUND ART

There is known a sensor apparatus which measures the properties orconstituents of an analyte liquid by detecting an object to be detectedcontained in the analyte liquid with use of a detecting element such asa surface acoustic wave device (refer to Patent Literatures 1 to 3, forexample).

For example, in a sensor apparatus employing a surface acoustic wavedevice, a reaction section which undergoes reaction with a componentcontained in a sample of an analyte liquid, is disposed on apiezoelectric substrate, and the properties or constituents of theanalyte liquid are detected by measuring variation in a surface acousticwave propagating through the reaction section. Such a measurement methodusing the surface acoustic wave device or the like has the advantageover other measurement methods (for example, enzymatic method) in thatit lends itself to simultaneous detection of a plurality ofcharacteristics to be measured.

However, such a conventional sensor apparatus is prone to losses ofsurface-acoustic-wave energy occurring at a boundary between thepiezoelectric substrate and a constituent component disposed on thepiezoelectric substrate, which results in difficulties in detecting anobject to be detected contained in an analyte with high sensitivity.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Publication JP-A5-240762 (1993)

Patent Literature 2: Japanese Unexamined Patent Publication JP-A2006-184011

Patent Literature 3: Japanese Unexamined Patent Publication JP-A2010-239477

SUMMARY OF INVENTION Technical, Problem

Thus, there is a demand for a sensor apparatus which is capable ofdetecting an object to be detected contained in an analyte liquid withexcellent sensitivity.

Solution to Problem

A sensor apparatus according to an embodiment of the invention includes:an element substrate; a detecting section disposed on an upper surfaceof the element substrate, the detecting section including a reactionsection having an immobilization film to detect an analyte; a first IDTelectrode configured to generate an acoustic wave which propagatestoward the reaction section, and a second IDT electrode configured toreceive the acoustic wave which has passed through the reaction section;and a protective film located on the upper surface of the elementsubstrate so as to cover the first IDT electrode, the second IDTelectrode, and at least part of the immobilization film, the protectivefilm extending between and contacting with the immobilization film andat least one of the first IDT electrode and the second IDT electrode.

Advantageous Effects of Invention

In accordance with the sensor apparatus according to the embodiment ofthe invention, in the element substrate, the protective film located onthe upper surface of the element substrate covers, in addition to thefirst IDT electrode and the second IDT electrode, at least part of theimmobilization film, the protective film extending between andcontacting with the immobilization film and at least one of the firstIDT electrode and the second IDT electrode. Accordingly, it is possibleto reduce losses of surface-acoustic-wave energy at a boundary betweenthe element substrate and a constituent component disposed on theelement substrate, and thereby detect an object to be detected containedin an analyte with high sensitivity.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C are views showing a sensor apparatus according to anembodiment of the invention, and FIG. 1A is a plan view, FIG. 1B is alengthwise sectional view, and FIG. 1C is a widthwise sectional view;

FIGS. 2A to 2E are exploded plan views of the sensor apparatus shown inFIGS. 1A to 1C;

FIGS. 3A to 3E are plan views showing procedural steps to manufacturethe sensor apparatus shown in FIGS. 1A to 10;

FIG. 4 is a plan view showing a detecting element of the sensorapparatus shown in FIGS. 1A to 10;

FIGS. 5A and 5B are sectional views showing the detecting element of thesensor apparatus shown in FIGS. 1A to 10;

FIGS. 6A and 6B are enlarged sectional views showing part of the sensorapparatus shown in FIGS. 5A and 5B; and

FIGS. 7A to 71 are schematic views showing procedural steps tomanufacture the detecting element.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of a sensor apparatus according to theinvention will be described with reference to drawings. In each drawingto be referred to in the following description, like constituent membersare identified with the same reference symbols. Moreover, for example,the size of each member and the distance between the individual membersare schematically shown in each drawing and may therefore differ fromthe actual measurements.

<Structure of Sensor Apparatus>

A sensor apparatus 100 according to an embodiment of the invention willbe described with reference to FIGS. 1A to 6B.

As shown in FIGS. 1A to 10, the sensor apparatus 100 according to theembodiment mainly comprises a first cover member 1, an intermediatecover member 1A, a second cover member 2, and a detecting element 3.

Specifically, as shown in FIG. 1B, the sensor apparatus 100 has an inletport 14 for admission of an analyte liquid, and a flow channel 15 whichis in communication with the inlet port 14, is surrounded by theintermediate cover member 1A and the second cover member 2, and extendsat least to a reaction section 13. In this embodiment, the intermediatecover member 1A and the second cover member 2 are greater in width thanthe detecting element 3. This allows an analyte liquid to flow so as tocover the entire surface of the detecting element 3 effectively.

FIG. 10 which shows sectional views of the construction shown in FIG.1A, wherein there are successively shown, in top-to-bottom order, asection taken along the line a-a, a section taken along the line b-b,and a section taken along the line c-c. The inlet port 14 is formed soas to pass through the second cover member 2 in a thickness directionthereof.

(First Cover Member 1)

As shown in FIGS. 1A, 1B and FIG. 2A, the first cover member 1 is shapedlike a flat plate. The thickness of the first cover member 1 falls inthe range of 0.1 mm to 1.5 mm, for example. The first cover member 1 hassubstantially a rectangular planar configuration. The longitudinallength of the first cover member 1 falls in the range of 1 cm to 8 cm,for example, and, the widthwise length of the first cover member 1 fallsin the range of 1 cm to 3 cm, for example.

As the material for forming the first cover member 1, for example, aglass-epoxy material, paper, plastics, celluloid, ceramics, non-wovenfabric, and glass can be used. The use of plastics is desirable from thestandpoints of required strength and cost.

Moreover, as shown in FIGS. 1A and 2A, on the upper surface of the firstcover member 1 are formed a terminal 6 and a wiring line 7 routed fromthe terminal 6 to a position near the detecting element 3.

The terminal 6 is formed on either side of the detecting element 3 in awidth direction on the upper surface of the intermediate cover member1A. Specifically, at least part of the terminals 6 arranged relative tothe detecting element 3 lies closer to the inlet port 14 than an inletport 14-side end of the detecting element 3. Moreover, in the range offour terminals 6 placed in an array on one side of the detecting element3 with respect to a direction longitudinally of the flow channel 15, thewiring lines 7 connected to two outer terminals 6, respectively, havesubstantially the same length, and, the wiring lines 7 connected to theother two inner terminals 6, respectively, have substantially the samelength. This makes it possible to reduce variations in signals obtainedby the detecting element 3 resulting from the difference in lengthbetween the wiring lines 7. In this case, with a construction in whichthe wiring lines 7 are connected so that a potential difference occursbetween grounding (earthing) wiring, which is constituted by one pair ofthe wiring lines 7 having substantially the same length, and signalwiring, which is constituted by the other pair of the wiring lines 7having substantially the same length, for example, upon application of apredetermined voltage from external measurement equipment to a first IDTelectrode 11 as shown in FIG. 4 via the wiring line 7, a firstextraction electrode 19, and so forth, it is possible to reduce thesignal variations, and thereby achieve an improvement in detectionreliability.

When measurement is made on the sensor apparatus 100 with externalmeasuring equipment (not shown in the drawing), the terminal 6 and theexternal measuring equipment are electrically connected to each other.Moreover, the terminal 6 and the detecting element 3 are electricallyconnected to each other via the wiring line 7, for example.

A signal issued from the external measuring equipment is inputted to thesensor apparatus 100 via the terminal 6, and, a signal issued from thesensor apparatus 100 is outputted to the external measuring equipmentvia the terminal 6.

(Intermediate Cover Member 1A)

In this embodiment, as shown in FIG. 1B, the intermediate cover member1A is placed in juxtaposition to the detecting element 3 on the uppersurface of the first cover member 1. Moreover, as shown in FIGS. 1A and3C, the intermediate cover member 1A and the detecting element 3 arearranged with a spacing. Note that the intermediate cover member 1A andthe detecting element 3 may be arranged with their sides kept in contactwith each other.

As shown in FIGS. 1B and 2B, the intermediate cover member 1A has theform of a flat frame constructed of a flat plate having a recess-formingarea 4, and, the thickness of the intermediate cover member 1A falls inthe range of 0.1 mm to 0.5 mm, for example.

In this embodiment, as shown in FIG. 1B, the recess-forming area 4 is anarea located downstream of a first upstream portion 1Aa. Theintermediate cover member 1A is joined to the flat plate-shaped firstcover member 1, whereupon an element placement section 5 is defined bythe first cover member 1 and the intermediate cover member 1A. That is,the upper surface of the first cover member 1 located inside therecess-forming area 4 becomes the bottom surface of the elementplacement section 5, and, the inner wall of the recess-forming area 4becomes the inner wall of the element placement section 5.

As shown in FIGS. 1A to 1C and 3A to 3E, in a region located downstreamof the detecting element 3, the intermediate cover member 1A does notexist on the first cover member 1. This makes it possible to inhibit orreduce generation of bubbles in a part of the intermediate cover member1A located downstream of the first upstream portion 1Aa. In consequence,an analyte liquid can be delivered in a bubble-free state onto thedetecting element 3, thus achieving an improvement in sensitivity oraccuracy in detection.

As the material for forming the intermediate cover member 1A, forexample, resin (including plastics), paper, non-woven fabric, and glasscan be used. More specifically, resin materials such as polyester resin,polyethylene resin, acrylic resin, and silicone resin are desirable foruse. The first cover member 1 and the intermediate cover member 1A maybe formed of either the same material or different materials.

Moreover, in this embodiment, the intermediate cover member 1A includesthe first upstream portion 1Aa. As shown in FIGS. 1A and 1B, when viewedfrom above, the detecting element 3 is located on the downstream siderelative to the first upstream portion 1Aa. In this case, when ananalyte liquid flows out over the detecting element 3 after passingthrough a part of the flow channel 15 which corresponds to the firstupstream portion 1Aa, an excess of the analyte liquid over an amount ofthe analyte liquid required for measurement flows downstream, whereforean adequate amount of the analyte liquid can be fed to the detectingelement 3.

(Second Cover Member 2)

As shown in FIGS. 1B and 3E, the second cover member 2 covers thedetecting element 3, and is joined to the first cover member 1 and theintermediate cover member 1A. As shown in FIGS. 1B and 10, the secondcover member 2 comprises a third substrate 2 a and a fourth substrate 2b.

As the material for forming the second cover member 2, for example,resin (including plastics), paper, non-woven fabric, and glass can beused. More specifically, resin materials such as polyester resin,polyethylene resin, acrylic resin, and silicone resin are desirable foruse. The first cover member 1 and the second cover member 2 may beformed of the same material. In this case, deformation resulting fromthe difference in thermal expansion coefficient between the first andsecond cover members can be minimized. The second cover member 2 mayeither be joined only to the intermediate cover member 1A or be joinedto both of the first cover member 1 and the intermediate cover member1A.

As shown in FIGS. 10, 3C, and 3D, the third substrate 2 a is bonded tothe upper surface of the intermediate cover member 1A. The thirdsubstrate 2 a is shaped like a flat plate having a thickness of 0.1 mmto 0.5 mm, for example. The fourth substrate 2 b is bonded to the uppersurface of the third substrate 2 a. The fourth substrate 2 b is shapedlike a flat plate having a thickness of 0.1 mm to 0.5 mm, for example.By joining the fourth substrate 2 b to the third substrate 2 a, as shownin FIG. 1B, the flow channel 15 is formed on the lower surface of thesecond cover member 2. The flow channel 15 extends from the inlet port14 to at least a region immediately above the reaction section 13, andhas a rectangular sectional profile, for example. The third substrate 2a and the fourth substrate 2 b may be formed of the same material, or,an unitary construction of the combined third and fourth substrates 2 aand 2 b may be used.

In this embodiment, as shown in FIG. 1B, neither the intermediate covermember 1A nor the third substrate 2 a exists at an end of the flowchannel 15, and, a gap left between the fourth substrate 2 b and thefirst cover member 1 serves as an air release hole 18. The air releasehole 18 is provided to let air and so forth present in the flow channel15 go out. The opening of the air release hole 18 may be given any shapewhich is capable of release of air present in the flow channel 15, andthus, for example, a circular shape or a rectangular shape may beadopted. For example, in the case of an air release hole 18 having acircular opening, the opening is designed to have a diameter of lessthan or equal to 2 mm, and, in the case of an air release hole 18 havinga rectangular shape, the air release hole 18 is designed so that eachside of the rectangle has a length of less than or equal to 2 mm.

The first cover member 1, the intermediate cover member 1A, and thesecond cover member 2 may be formed of the same material. In this case,since these members are substantially uniform in thermal expansioncoefficient, it is possible to reduce deformation of the sensorapparatus 100 caused by the difference in thermal expansion coefficientamong the members. Moreover, in the case of application of a biomaterialto the reaction section 13, some biomaterials are prone to qualitydegradation under external light such as ultraviolet rays. In thisregard, it is advisable to use an opaque material having light-blockingcapability as the material for forming the first cover member 1, theintermediate cover member 1A, and the second cover member 2. On theother hand, when the reaction section 13 is substantially free ofexternal light-induced quality degradation, the second cover member 2constituting the flow channel 15 may be formed of a nearly transparentmaterial. In this case, the condition of an analyte liquid flowingthrough the interior of the flow channel 15 can be visually checked,thus permitting the combined use of an optical detection system.

(Detecting Element 3)

The detecting element 3 in the present embodiment will be described withreference to FIGS. 1A to 6B, in particular, FIGS. 4 to 6B.

FIGS. 6A and 6B are enlarged sectional views showing part of the sensorapparatus shown in FIGS. 5A and 5B, and more specifically FIG. 6A is anenlarged view of the principal portion of the detecting element shown inFIG. 5B, and FIG. 6B is an enlarged view of part of the principalportion shown in FIG. 6A.

As shown in FIGS. 6A and 6B, the detecting element 3 generally comprisesan element substrate 10 a disposed on the upper surface of the firstcover member 1, and at least one detecting section 10 b, disposed on theupper surface of the element substrate 10 a, for detecting an object tobe detected (detection target) contained in an analyte liquid.

Specifically, as shown in FIGS. 6A and 6B, the detecting element 3 inthis embodiment comprises: the element substrate 10 a; the detectingsection 10 b disposed on the upper surface of the element substrate 10a, the detecting section 10 b including the reaction section 13 havingan immobilization film 13 a to detect an object to be detected, a firstIDT (InterDigital Transducer) electrode 11 configured to generate anacoustic wave which propagates toward the reaction section 13, and asecond IDT electrode 12 configured to receive the acoustic wave whichhas passed through the reaction section 13; and a protective film 28located on the upper surface of the element substrate 10 a so as tocover the first IDT electrode 11, the second IDT electrode 12, and atleast part of the immobilization film 13 a, the protective film 28extending between and contacting with the immobilization film 13 a andat least one of the first IDT electrode 11 and the second IDT electrode12.

The detecting section 10 b includes, in addition to the first IDTelectrode 11, the reaction section 13, and the second IDT electrode 12,the protective film 28, a first extraction electrode 19, a secondextraction electrode 20, and so forth.

(Element Substrate 10 a)

The element substrate 10 a is constructed of a substrate of singlecrystal having piezoelectric properties such for example as quartz,lithium tantalate (LiTaO₃) single crystal, or lithium niobate (LiNbO₃)single crystal. The planar configuration and dimensions of the elementsubstrate 10 a are suitably determined. The element substrate 10 a has athickness of 0.3 mm to 1 mm, for example.

In this embodiment, a surface roughness of the upper surface of theimmobilization film 13 a is greater than a surface roughness of a regionwhere the immobilization film 13 a is located in the element substrate10 a. In this case, for example, in immobilizing aptamers andantibodies, which will hereafter be described, onto the surface of theelement substrate 10 a, it is possible to increase bindability of theaptamers and antibodies to the surface of the immobilization film 13 a,thus enabling high-density immobilization. This makes it possible toimprove detection sensitivity of the object to be detected.

(IDT Electrodes 11 and 12)

As shown in FIGS. 4, 6A and 6B, the first IDT electrode 11 comprises apair of comb electrodes. Each comb electrode includes two bus barsopposed to each other and a plurality of electrode fingers 11 a to lie(11 a, 11 b, 11 c, 11 d, and 11 e) each extending from corresponding oneof the bus bars toward the other. A pair of the comb electrodes isdisposed so that the plurality of electrode fingers 11 a to 11 e arearranged in an interdigitated pattern. The second IDT electrode 12 issimilar in configuration to the first IDT electrode 11. The first IDTelectrode 11 and the second IDT electrode 12 constitute a transversalIDT electrode.

The first IDT electrode 11 is intended for generation of predeterminedsurface acoustic wave (SAW), and the second IDT electrode 12 is intendedfor reception of the SAW generated in the first IDT electrode 11. Thefirst IDT electrode 11 and the second IDT electrode 12 are positioned onthe same straight line so that the SAW generated in the first IDTelectrode 11 can be received by the second IDT electrode 12. Frequencyresponse characteristics can be designed on the basis of the number ofthe electrode fingers of the first IDT electrode 11 and the second IDTelectrode 12, the distance between the adjacent electrode fingers, thecrossing width of the electrode fingers, etc., used as parameters.

There are various modes of vibration for SAW to be excited by the IDTelectrode. In the detecting element 3 according to the embodiment, forexample, a vibration mode of transversal waves called SH waves isutilized. The frequency of SAW may be set within the range of severalmegahertz (MHz) to several gigahertz (GHz), for example. It is advisableto set the SAW frequency within the range of several hundred MHz to 2GHz from the practicality standpoint, and also in the interest ofminiaturization of the detecting element 3 that will eventually beconducive to miniaturization of the sensor apparatus 100. Thethicknesses and lengths of predetermined constituent elements in theembodiment will be described with respect to the case where the centerfrequency of SAW falls in a several hundred MHz range.

The first IDT electrode 11 and the second IDT electrode 12 may be of asingle-layer structure composed of, for example, a gold thin layer, ormay be of a multilayer structure such as a three-layer structurecomposed of a titanium layer, a gold layer, and a titanium layer, or athree-layer structure composed of a chromium layer, a gold layer, and achromium layer, in the order named, from the element-substrate 10 aside.

A thickness of the first IDT electrode 11 and the second IDT electrode12 may be set to fall within the range of 0.005λ to 0.015λ, for example.

An elastic member may be disposed externally of the first IDT electrode11 and the second IDT electrode 12 in a SAW propagation direction (widthdirection) to reduce SAW reflection.

(Reaction Section 13)

As shown in FIGS. 4, 6A and 6B, the reaction section 13 is disposedbetween the first IDT electrode 11 and the second IDT electrode 12.

In this embodiment, the reaction section 13 comprises the immobilizationfilm 13 a (for example, a metallic film) formed on the upper surface ofthe element substrate 10 a, and a reactant immobilized on the uppersurface of the immobilization film 13 a for reaction with an object tobe detected. The reactant is suitably selected depending on an object tobe detected which is a detection target. For example, when the object tobe detected is a specific cell or living tissue present in an analyteliquid, an aptamer composed of a nucleic acid or a peptide can be usedas the reactant. For example, in this embodiment, while a reactionbetween the reactant and the object to be detected may be a bindingreaction of the object to be detected and the reactant such as achemical reaction or an antigen-antibody reaction, the reaction is notso limited, but may be a binding reaction of the object to be detectedand the reactant under the interaction of the object to be detected withthe reactant, or an adsorption reaction of the object to be detected tothe reactant. Exemplary of a reactant which can be used for the reactionsection 13 in the embodiment is one which causes, by its presence,variation in surface-acoustic-wave characteristics according to the typeor content of the object to be detected when an analyte is brought intocontact with the reaction section 13. The reaction section 13 isintended for causing reaction with an object to be detected contained inan analyte liquid, and, more specifically, upon contact of an analyteliquid with the reaction section 13, a specific object to be detectedcontained in the analyte liquid is bound to an aptamer adapted to theobject to be detected.

The immobilization film 13 a (metallic film) may be of a single-layerstructure composed of, for example, a gold layer, or may be of amultilayer structure such as a two-layer structure composed of atitanium layer and a gold layer situated on the titanium layer or atwo-layer structure composed of a chromium layer and a gold layersituated on the chromium layer. Moreover, the immobilization film 13 amay be formed of the same material as a material used for the first IDTelectrode 11 and the second IDT electrode 12. In this case, theimmobilization film 13 a and the first and second IDT electrodes 11 and12 can be formed in the same process step. Instead of theabove-mentioned metallic film, for example, an oxide film such as a SiO₂film or TiO₂ film may be used as the material of construction of theimmobilization film 13 a.

Given that the first IDT electrode 11, the second IDT electrode 12, andthe reaction section 13 arranged in the width direction of the flowchannel are grouped into a set, then, as shown in FIG. 4, two sets areprovided in the sensor apparatus 100 according to the embodiment. Inthis case, by designing the reaction section 13 of one of the sets andthe reaction section 13 of the other to undergo reaction with differentdetection targets, it is possible to detect two different objects to bedetected by a single sensor apparatus.

In this embodiment, as shown in FIGS. 6A and 6B, the upper surface ofthe immobilization film 13 a comprises regions 13 a 1 which are coveredwith the protective film 28 and are at ends of the side of the first IDTelectrode 11 and the side of the second IDT electrode 12, respectively,and a region 13 a 2 of a center part which is not covered with theprotective film 28. An upper surface of the region 13 a 1 which iscovered with the protective film 28 is at a higher level than an uppersurface of the region 13 a 2 which is not covered with the protectivefilm 28. In this case, in the reaction section 13, energy of SAWpropagating between the first IDT electrode 11 and the second IDTelectrode 12 tends to be further concentrated on the upper surface ofthe region 13 a 2 which is not covered with the protective film 28 inthe upper surface of the immobilization film 13 a, wherefore an objectto be detected can be detected with high sensitivity. As a specificexample, as shown in FIG. 6B, the upper surface of the immobilizationfilm 13 a may be so inclined that a level of the upper surface becomeslower as approaching from the region 13 a 1 which is covered with theprotective film 28 to the region 13 a 2 which is not covered with theprotective film 28.

In this embodiment, as shown in FIG. 6B, the upper surface of the region13 a 1 which is covered with the protective film 28 in the upper surfaceof the immobilization film 13 a is at substantially the same level as atleast one of the upper surface of the first IDT electrode 11 and theupper surface of the second IDT electrode 12. This makes it possible toreduce losses of energy when SAW propagating through the elementsubstrate 10 a is transmitted from the first IDT electrode 11 via theimmobilization film 13 a to the second IDT electrode 12.

Moreover, the upper surface of the region 13 a 2 which is not coveredwith the protective film 28 in the upper surface of the immobilizationfilm 13 a is at a lower level than at least one of the upper surface ofthe first IDT electrode 11 and the upper surface of the second IDTelectrode 12. In this case, in the reaction section 13, energy of SAWpropagating between the first IDT electrode 11 and the second IDTelectrode 12 tends to be concentrated on the upper surface of theimmobilization film 13 a, wherefore an object to be detected can bedetected with even higher sensitivity.

In this embodiment, as shown in FIG. 6B, a thickness of the region 13 a1 which is covered with the protective film 28 of the immobilizationfilm 13 a is greater than a thickness of the region 13 a 2 which is notcovered with the protective film 28 thereof. In the immobilization film13 a, given that the wavelength of SAW propagating between the first IDTelectrode 11 and the second IDT electrode 12 is A, then a thickness ofthe region 13 a 1 which is covered with the protective film 28 may beset to fall within, for example, the range of 0.005λ to 0.015λ, and, forexample, and a thickness of the region 13 a 2 which is not covered withthe protective film 28 may be set to be 0.01λ or below smaller than thethickness of the region 13 a 1 which is covered with the protective film28, and may thus be set to fall within the range of 0.004λ to 0.014λ. Inthis case, even if the region 13 a 2 which is not covered with theprotective film 28 of the immobilization film 13 a has a relativelysmall thickness, in the reaction section 13, losses of energy of SAWpropagating between the first IDT electrode 11 and the second IDTelectrode 12 can be reduced. In addition to that, since the SAW energytends to be concentrated on the upper surface of the region 13 a 2 whichis not covered with the protective film 28 of the immobilization film 13a, it is possible to detect an object to be detected with even highersensitivity. As a specific example, as shown in FIG. 6B, theimmobilization film 13 a may be so shaped that its thickness becomessmaller as approaching from the region 13 a 1 which is covered with theprotective film 28 to the region 13 a 2 which is not covered with theprotective film 28.

In this embodiment, the surface roughness of the upper surface of theregion 13 a 2 which is not covered with the protective film 28 in theupper surface of the immobilization film 13 a is greater than thesurface roughness of the upper surface of the first IDT electrode 11 andthe surface roughness of the upper surface of the second IDT electrode12. In this case, since the surface area of the immobilization film 13 acan be increased, it is possible to immobilize reactants such asaptamers and antibodies onto the immobilization film 13 a at highdensities, and thereby improve detection sensitivity of the object to bedetected. a surface roughness of the upper surface of the region 13 a 2which is not covered with the protective film 28 in the upper surface ofthe immobilization film 13 a may be set to fall within the range of 2.0to 10.0 nm, for example, in terms of arithmetic average roughness Ra.The surface roughness of each constituent element may be determined bymeasurement using arithmetic average roughness Ra. In the case where afilm or the like is disposed on a measurement target, for example,graphic analyses of the sectional profile of the measurement target areperformed on the basis of a photograph of the section obtained by meansof SEM (Scanning Electron Microscopy), TEM (Transmission ElectronMicroscopy), or otherwise, for surface roughness measurement. Moreover,when direct measurement of the measurement target is possible, themeasurement may be effected with use of a commonly-usedsurface-roughness meter of contact type or non-contact type.

Moreover, it is advisable that the surface roughness of the uppersurface of the region 13 a 1 which is covered with the protective film28 in the upper surface of the immobilization film 13 a is substantiallyequal to the surface roughness of the upper surface of the first IDTelectrode 11 and the surface roughness of the upper surface of thesecond IDT electrode 12. This makes it possible to render theimmobilization film 13 a, the first IDT electrode 11, and the second IDTelectrode 12 uniform in bondability to the protective film 28.

(Protective Film 28)

As shown in FIGS. 6A and 6B, the protective film 28 is located on theupper surface of the element substrate 10 a so as to cover the first IDTelectrode 11 and the second IDT electrode 12. This makes it possible toinhibit an analyte liquid from contact with the first IDT electrode 11and the second IDT electrode 12, and thereby retard corrosion of the IDTelectrodes caused by oxidation, for example. Examples of materials usedfor the protective film 28 include silicon oxide, aluminum oxide, zincoxide, titanium oxide, silicon nitride, and silicon. Such a material isproperly used as a major constituent, namely a component constitutingthe greatest proportion in mass, of a material for forming theprotective film 28, and is therefore not defined as the constituentmaterial when mixed merely as impurities in very small amounts, forexample.

Moreover, in this embodiment, as shown in FIGS. 6A and 6B, theprotective film 28 also covers at least part of the immobilization film13 a, and extends between and contacts with the immobilization film 13 aand at least one of the first IDT electrode 11 and the second IDTelectrode 12. This makes it possible to reduce losses of SAW energy atan interface between the element substrate 10 a and a constituentcomponent disposed on the element substrate 10 a, and thereby detect anobject to be detected contained in an analyte with high sensitivity. Asa specific example, as shown in FIG. 6B, the protective film 28 coversthe ends of the immobilization film 13 a located on the side of thefirst IDT electrode 11 and the side of the second IDT electrode 12. Thismakes it possible to inhibit an analyte liquid from contact with the endof the immobilization film 13 a and thereby retard corrosion caused forexample by oxidation, as well as to immobilize reactants such asaptamers and antibodies onto the central region 13 a 2 of theimmobilization film 13 a which is not covered with the protective film28 and thereby ensure detection sensitivity of the object to bedetected.

In this embodiment, as shown in FIG. 6B, the protective film 28 extendsbetween and contact with the immobilization film 13 a and at least oneof the first IDT electrode 11 and the second IDT electrode 12. As aspecific example, as shown in FIG. 6B, the protective film 28 isdisposed so as to thoroughly fill the gap between the immobilizationfilm 13 a and the first, second IDT electrode 11, 12 disposed on theelement substrate 10 a. In this case, the interposition of theprotective film 28 between the immobilization film 13 a and the first,second IDT electrode 11, 12 makes it possible to suppress acousticimpedance variation, and thereby minimize the influence of reflectedwaves entailed by the placement of other member, with consequentreduction in SAW energy losses.

As shown in FIGS. 4, 6A and 6B, the first IDT electrode 11 and thesecond IDT electrode 12 include a plurality of electrode fingers 11 a to11 e and the plurality of electrode fingers 12 a to 12 e (12 a, 12 b, 12c, 12 d, and 12 e) which are spaced apart from each other, respectively,and, as shown in FIG. 6B, the protective film 28 is made in continuous(connected) form so as to lie over, out of the plurality of electrodefingers 11 a to lie, as well as 12 a to 12 e, two adjacent electrodefingers, for example, the electrode fingers 11 a and 11 b, as well as 12a and 12 b, and also over that part of the element substrate 10 alocated between the two electrode fingers 11 a and 11 b, as well as 12 aand 12 b. This makes it possible to inhibit occurrence ofshort-circuiting between the plurality of electrode fingers of the IDTelectrode caused by an analyte liquid.

Moreover, as shown in FIG. 6B, an end of the protective film 28 locatedon a side of the reaction section 13 (the immobilization film 13 a)comprises a lower end part and an upper end part, the lower end partbeing closer to a center part of the reaction section 13 (theimmobilization film 13 a) than the upper end part when viewed in alateral section. As used herein, the language “lateral section” means,as will be seen from FIG. 1B for example, a section taken along the linea-a of FIG. 1A or a line perpendicular to the line a-a, looking from theside of the sensor apparatus. Moreover, the language “end located on aside of the reaction section 13” means an end of the protective film 28opposite the end located toward at least one of the first IDT electrode11 and the second IDT electrode 12 under the condition where, forexample, as described above, the protective film 28 lies also in betweenthe reaction section 13 and at least one of the first IDT electrode 11and the second IDT electrode 12, and does not cover the entire area ofthe reaction section 13. Furthermore, as shown in FIG. 6B, an end of theprotective film 28 located on the side of the reaction section 13 (theimmobilization film 13 a) comprises a lower end part and an upper endpart, the end being inclined so that the distance between the end and acenter part of the reaction section 13 (the immobilization film 13 a)becomes shorter as the end going from the upper end part to the lowerend part when viewed in a lateral section. This makes it possible toinhibit an analyte liquid from contact with the first IDT electrode 11and the second IDT electrode 12 more effectively. Moreover, by formingthe protective film 28 so as to cover the upper surface of the elementsubstrate 10 a, it is possible to enhance stability of connection withthe element substrate 10 a.

In this embodiment, a thickness of the protective film 28 may be set tofall within the range of 0.001λ to 0.05λ, for example. While thethickness of the protective film 28 may be measured in a part of theprotective film 28 which covers neither the first IDT electrode 11 northe second IDT electrode 12, the measurement in other part will not beexcluded herein.

As an alternative to the configuration as shown in FIGS. 6A and 6B justdescribed, a thickness of the protective film 28 may be smaller than thethickness of the first IDT electrode 11 and the thickness of the secondIDT electrode 12. This makes it possible to reduce the influence of theprotective film 28 upon SAW propagating between the first IDT electrode11 and the second IDT electrode 12, and thereby reduce losses of SAWenergy. In this case, the upper surface of the protective film 28 maybe, at least partly, positioned at a level lower than the upper surfaceof the first IDT electrode 11 and the upper surface of the second IDTelectrode 12.

(Extraction Electrodes 19 and 20)

As shown in FIG. 4, the first extraction electrode 19 is connected tothe first IDT electrode 11, and the second extraction electrode 20 isconnected to the second IDT electrode 12. The first extraction electrode19 is extracted from the first IDT electrode 11 in the oppositedirection to the reaction section 13, and, an end 19 e of the firstextraction electrode 19 is electrically connected to the wiring line 7disposed in the first cover member 1. The second extraction electrode 20is extracted drawn from the second IDT electrode 12 in the oppositedirection to the reaction section 13, and, an end 20 e of the secondextraction electrode 20 is electrically connected to the wiring line 7.

The first extraction electrode 19 and the second extraction electrode 20may be made similar in material and configuration to the first IDTelectrode 11 and the second IDT electrode 12, and may thus be of asingle-layer structure composed of, for example, a gold thin layer, ormay be of a multilayer structure such as a three-layer structurecomposed of a titanium layer, a gold layer, and a titanium layer, or athree-layer structure composed of a chromium layer, a gold layer, and achromium layer, in the order named, from the element-substrate 10 aside.

(Detection of Detection Target Using Detecting Element 3)

In the process of detection of an object to be detected contained in ananalyte liquid by the detecting element 3 that utilizes SAW as abovedescribed, the first step is to apply a predetermined voltage fromexternal measuring equipment to the first IDT electrode 11 via thewiring line 7, the first extraction electrode 19, and so forth.

Upon the voltage application, on the surface of the element substrate 10a, the first IDT electrode 11-forming region is excited, thus producingSAW having a predetermined frequency. Part of the SAW so generatedpropagates toward the reaction section 13, passes through the reactionsection 13, and reaches the second IDT electrode 12. In the reactionsection 13, the aptamer on the reaction section 13 is bound to aspecific object to be detected contained in the analyte liquid, and theweight (mass) of the reaction section 13 changes correspondingly, whichresults in variation in the characteristics, such as a phase, of the SAWpassing through the reaction section 13. In response to the arrival ofthe SAW having varied characteristics at the second IDT electrode 12, acorresponding voltage is developed in the second IDT electrode 12.

The thereby developed voltage is outputted through the second extractionelectrode 20, the wiring line 70, and so forth. By reading the outputwith external measuring equipment, it is possible to examine theproperties and constituents of the analyte liquid.

In the sensor apparatus 100, capillarity is utilized to direct theanalyte liquid to the reaction section 13.

Specifically, as described earlier, when the second cover member 2 isjoined to the intermediate cover member 1A, as shown in FIGS. 1A to 10,the flow channel 15 is defined, in the form of a narrow elongate pipe,on the lower surface of the second cover member 2. Thus, by setting, forexample, the width or the diameter of the flow channel 15 at apredetermined value with consideration given to the type of the analyteliquid, the materials of construction of the intermediate cover member1A and the second cover member 2, and so forth, it is possible to causecapillarity in the flow channel 15 in the form of a narrow elongatepipe. For example, the flow channel 15 has a width of 0.5 mm to 3 mm,and a depth of 0.1 mm to 0.5 mm. As shown in FIG. 1B, the flow channel15 has a downstream portion (extension) 15 b which is a portionextending beyond the reaction section 13, and, the second cover member 2is formed with the air release hole 18 which is in communication withthe extension 15 b. Upon admission of the analyte liquid into the flowchannel 15, air present in the flow channel 15 is expelled out of theair release hole 18.

With such a pipe form capable of causing capillarity defined by thecover members including the intermediate cover member 1A and the secondcover member 2, upon contact with the inlet port 14, the analyte liquidis drawn into the interior of the sensor apparatus 100 while passingthrough the flow channel 15. Thus, the sensor apparatus 100 has ananalyte liquid suction mechanism built in itself, and is thereforecapable of analyte liquid suction without using an instrument such as apipette.

(Positional Relationship Between Flow Channel 15 and Detecting Element3)

In this embodiment, while the analyte-liquid flow channel 15 has a depthof about 0.3 mm, the detecting element 3 has a thickness of about 0.3mm, that is; as shown in FIG. 1B, the depth of the flow channel 15 andthe thickness of the detecting element 3 are substantially equal.Therefore, if the detecting element 3 is placed as it is on the uppersurface of the first cover member 1, the flow channel 15 will beblocked. In this regard, in the sensor apparatus 100, as shown in FIGS.1B, 5A and 5B, the element placement section 5 is defined by the firstcover member 1 on which the detecting element 3 is mounted, and theintermediate cover member 1A joined onto the first cover member 1. Thedetecting element 3 is housed in this element placement section 5 sothat the analyte-liquid flow channel 15 will not be blocked. That is,the depth of the element placement section 5 is adjusted to besubstantially equal to the thickness of the detecting element 3, and,the detecting element 3 is mounted inside the element placement section5. Thereby, the flow channel 15 can be provided.

The detecting element 3 is secured to the bottom surface of the elementplacement section 5 by, for example, a die-bonding material composedpredominantly of resin such as epoxy resin, polyimide resin, or siliconeresin.

The end 19 e of the first extraction electrode 19 and the wiring line 7are electrically connected to each other by a metallic narrow wire 27formed of, for example, Au. The connection between the end 20 e of thesecond extraction electrode 20 and the wiring line 7 is made in asimilar way. Means for connecting the wiring line 7 with the first andsecond extraction electrodes 19 and 20 is not limited to the metallicnarrow wire 27, but may be of an electrically-conductive adhesive suchas a Ag paste. Since a gap is left in the part where the wiring line 7makes connection with each of the first and second extraction electrodes19 and 20, it is possible to suppress damage of the metallic narrow wire27 when bonding the second cover member 2 to the first cover member 1.Moreover, the first extraction electrode 19, the second extractionelectrode 20, the metallic narrow wire 27, and the wiring line 7 arecovered with the protective film 28. By covering the first extractionelectrode 19, the second extraction electrode 20, the metallic narrowwire 27, and the wiring line 7 with the protective film 28, it ispossible to suppress corrosion of these electrodes and the like.

As described heretofore, according to the sensor apparatus 100 in theembodiment, by placing the detecting element 3 in the element placementsection 5 of the first cover member 1, it is possible to provide theanalyte-liquid flow channel 15 extending from the inlet port 14 to thereaction section 13, and thereby allow the analyte liquid, which hasbeen drawn into the apparatus through the inlet port 14 undercapillarity for example, to flow to the reaction section 13. That is,even with use of the detecting element 3 having a certain thickness,since the sensor apparatus 100 has an analyte liquid suction mechanismbuilt in itself, it is possible to provide a sensor apparatus 100capable of directing an analyte liquid to the detecting element 3efficiently.

<Manufacturing Process of Detecting Element>

The following describes a procedure in the making of the detectingelement 3 provided in the sensor apparatus 100 according to theembodiment of the invention. FIGS. 7A to 71 are schematic views showingprocedural steps for manufacturing the detecting element 3.

First, a quartz-made element substrate 10 a is washed. After that, on anas needed basis, an Al film is formed on the lower surface of theelement substrate 10 a by RF sputtering technique (FIG. 7A).

Next, an electrode pattern is formed on the upper surface of the elementsubstrate 10 a. In this step, a photoresist pattern 51 of image reversaltype for electrode-pattern formation is formed by photolithographytechnique (FIG. 7B).

Next, a metallic layer 52 having a three-layer structure composed ofTi/Au/Ti layers is formed on each of a photoresist pattern 51-bearingpart and a photoresist pattern 51-free part of the upper surface of theelement substrate 10 a by electron-beam vapor deposition equipment (FIG.7C).

Next, a Ti/Au/Ti electrode pattern 53 is formed by lifting off thephotoresist pattern 51 using a solvent, followed by oxygen-plasma ashingtreatment (FIG. 7D). In this embodiment, the Ti/Au/Ti electrode pattern53 constitutes, in addition to a pair of IDT electrodes 11 and 12,immobilization film 13 a, a reflector and mounting extraction electrodes19 and 20. The pair of IDT electrodes 11 and 12 are disposed so as toface each other, and, one of them serves as a transmitter, whereas theother serves as a receiver.

Next, a protective film 28 is formed on the upper surface of the elementsubstrate 10 a so as to cover the Ti/Au/Ti electrode pattern 53 by, forexample, TEOS (Tetra Ethyl Ortho Silicate)-plasma CVD technique (FIG.7E).

Next, a protective film 28 pattern is defined by first forming apositive photoresist 54 on the upper surface of the protective film 28,followed by etching of the protective film 28 using RIE equipment (FIG.7F). Specifically, the positive photoresist 54 is formed on a part ofthe protective film 28 which covers the IDT electrodes 11 and 12 andpart of the immobilization film 13 a, and, following the completion ofetching of other part free of the photoresist 54 using the RIEequipment, the photoresist 54 is lifted off with use of a solvent,whereupon the protective film 28 pattern for covering the IDT electrodes11 and 12 and part of the immobilization film 13 a is formed. Note that,by removing the protective film 28 from a photoresist 54-free part ofthe Ti/Au/Ti electrode pattern 53 by etching using the RIE equipment,and subsequently etching the outermost Ti layer of the electrodepattern, a part of the immobilization film 13 a which is not coveredwith the protective film 28 may be given a two-layer structure composedof Au/Ti layers. In consequence, the immobilization film 13 a having atwo-layer structure composed of Au/Ti layers is located between thepaired IDT electrodes 11 and 12. Given that the pair of IDT electrodes11 and 12 and the immobilization film 13 a of Au/Ti two-layer structureare grouped into a set, then there are provided two sets on a singlesensor, and, one of the two sets is used as a set for detection, whereasthe other is used as a set for reference.

After that, the Al film 50 formed on the lower surface of the elementsubstrate 10 a is removed with use of fluonitric acid.

An aptamer composed of a nucleic acid or a peptide is immobilized on theupper surface of the immobilization film 13 a to form the reactionsection 13 (FIG. 7G).

In the manner as described heretofore, the detecting element 3 isformed.

Next, the element substrate 10 a is cut in a predetermined size bydicing (FIG. 7H). After that, separate detecting elements 3 obtained bycutting process are fixedly attached, at their back sides, onto awiring-equipped glass epoxy mounting substrate (hereafter referred to as“mounting substrate”) corresponding to the first cover member 1 with useof an epoxy adhesive. Then, a Au narrow wire used as the lead wire 27 isset to provide electrical connection between the wiring line 7 connectedto the terminal 6 disposed on the mounting substrate and the end 19 e,20 e of the extraction electrode disposed on the detecting element 3(FIG. 7I).

Following the completion of placement of the intermediate cover member1A, the second cover member 2, and so forth, the sensor apparatus 100according to an embodiment of the invention is formed.

The manufacturing process of the detecting element 3, as well as themanufacturing process of the sensor apparatus 100, is not limited to theaforestated procedure shown in FIGS. 7A to 71, and it is thus possibleto adopt any other manufacturing process that enables production of theelement substrate 10 a whose upper surface is configured so that theregion 10 a 2 where the reaction section 13 is located is lower than theregions 10 a 1 where the first IDT electrode 11 and the second IDTelectrode 12 are located.

The invention is not limited to the embodiment thus far described, andmay therefore be carried into effect in various forms.

Although the reaction section 13 in the aforestated embodiment has beenillustrated as comprising the immobilization film 13 a and the aptamerimmobilized on the upper surface of the immobilization film 13 a, theinvention is not limited to the aptamer, and thus, as an alternative, areactant which undergoes reaction with an object to be detectedcontained in an analyte liquid and causes variation in SAWcharacteristics before and after analyte passage through the reactionsection 13 may be immobilized on the upper surface of the immobilizationfilm 13 a. Moreover, for example, in the case where the object to bedetected in the analyte liquid reacts with the immobilization film 13 a,the reaction section 13 may be composed solely of the immobilizationfilm 13 a without using a reactant such as the aptamer. Moreover, anon-conductive film may be used as the immobilization film 13 a insteadof a metallic film, and the aptamer may be immobilized on the uppersurface of the non-conductive film.

Moreover, the detecting element 3 may be constructed of a singlesubstrate on which a variety of devices are disposed. For example, anenzyme electrode for use with enzyme electrode method may be disposednext to a SAW device. In this case, in addition to measurement based onthe immuno method using an antibody or aptamer, measurement based on theenzymatic method can also be conducted, thus increasing the number ofmeasurement points that can be checked at one time.

Moreover, while the embodiment has been described with respect to thecase of providing a single detecting element 3, a plurality of detectingelements 3 may be provided. In this case, the element placement section5 is formed for each detecting element 3 on an individual basis, or, theelement placement section 5 is configured to have a length or widthlarge enough to receive all of the detecting elements 3.

Moreover, while the embodiment has been described with respect to thecase where the first cover member 1, the intermediate cover member 1A,and the second cover member 2 are provided as separate components, thisdoes not constitute any limitation, and thus either a combination ofsome of these members in an unitary structure or a combination of allthe members in an unitary structure may be adopted.

REFERENCE SIGNS LIST

-   -   1: First cover member    -   1A: Intermediate cover member    -   1Aa: First upstream portion    -   2: Second cover member    -   2 a: Third substrate    -   2 b: Fourth substrate    -   3: Detecting element    -   4: Recess-forming area    -   5: Element placement section    -   6: Terminal    -   7: Wiring line    -   9: Filler member    -   10 a: Element substrate    -   10 b: Detecting section    -   11: First IDT electrode    -   12: Second IDT electrode    -   13: Reaction section    -   13 a: Immobilization film    -   14: Inlet port    -   15: Flow channel    -   15 a: Upstream portion    -   15 b: Downstream portion (extension)    -   18: Air release hole    -   19: First extraction electrode    -   19 e: End    -   20: Second extraction electrode    -   20 e: End    -   27: Lead wire (metallic narrow wire)    -   28: Protective film    -   100: Sensor apparatus

1. A sensor apparatus, comprising: an element substrate; and a detectingsection on the element substrate, the detecting section comprising afirst IDT electrode, a second IDT electrode, and a reaction sectionsandwiched by the first IDT electrode and the second IDT electrode, andhaving an immobilization film, the immobilization film comprising aportion having a smaller thickness than thicknesses of the first IDTelectrode and the second IDT electrode.
 2. The sensor apparatusaccording to claim 1, wherein the element substrate is constructed of asubstrate of single crystal.
 3. The sensor apparatus according to claim1, wherein a material of the immobilization film is a same as a materialof the first IDT electrode and a material of the second IDT electrode.4. The sensor apparatus according to claim 1, wherein the immobilizationfilm has a first multilayer structure in which a plurality of layers arestacked on the upper surface of the element substrate.
 5. The sensorapparatus according to claim 1, wherein the first IDT electrode and thesecond IDT electrode each have a second multilayer structure in which aplurality of layers are staked on the upper surface of the elementsubstrate.
 6. The sensor apparatus according to claim 1, wherein theimmobilization film has a first multilayer structure in which aplurality of layers are stacked on the upper surface of the elementsubstrate, the first IDT electrode and the second IDT electrode eachhave a second multilayer structure in which a plurality of layers arestaked on the upper surface of the element substrate, and the firstmultilayer structure is different from the second multilayer structure.7. The sensor apparatus according to claim 1, wherein the immobilizationfilm has a first multilayer structure in which a plurality of layers arestacked on the upper surface of the element substrate, the first IDTelectrode and the second IDT electrode each have a second multilayerstructure in which a plurality of layers are staked on the upper surfaceof the element substrate, in the first multilayer structure, a titaniumlayer and a gold layer are successively stacked on the upper surface ofthe element substrate, in the second multilayer structure, a titaniumlayer, a gold layer and a titanium layer are successively stacked on theupper surface of the element substrate.
 8. The sensor apparatusaccording to claim 1, wherein the immobilization film comprises ametallic film located on the upper surface of the element substrate. 9.The sensor apparatus according to claim 1, wherein the immobilizationfilm comprises an oxide film located on the upper surface of the elementsubstrate.
 10. The sensor apparatus according to claim 1, wherein asurface roughness of a region on which the immobilization film islocated in the upper surface of the element substrate is smaller than asurface roughness of an upper surface of the immobilization film. 11.The sensor apparatus according to claim 1, further comprising: aprotective member located on the upper surface of the element substrate,at least part of the protective member contacting with theimmobilization film, the first IDT electrode, and the second IDTelectrode.
 12. The sensor apparatus according to claim 11, wherein theprotective member covers ends of the immobilization film located on aside of the first IDT electrode and a side of the second IDT electrode.13. The sensor apparatus according to 12, wherein an upper surface ofthe immobilization film comprises a first region which is covered withthe protective member and is located on the end of the immobilizationfilm on the side of the first IDT electrode, a second region which iscovered with the protective member and is located on the end of theimmobilization film on the side of the second IDT electrode, and a thirdregion located on a center part of the immobilization film which is notcovered with the protective member.
 14. The sensor apparatus accordingto claim 13, wherein the upper surface of the immobilization film isinclined so that a level of the upper surface of the immobilization filmgradually becomes lower as approaching from the first region and/or thesecond region to the third region.
 15. The sensor apparatus according toclaim 11, wherein in an upper surface of the immobilization film, aregion which is not covered with the protective member is at a lowerlevel than a level of at least one of an upper surface of the first IDTelectrode and an upper surface of the second IDT electrode.
 16. Thesensor apparatus according to claim 13, wherein a thickness of theimmobilization film gradually becomes smaller as approaching from thethird region to the first region and/or the second region.
 17. Thesensor apparatus according to claim 11, wherein a surface roughness of aregion which is not covered with the protective member in an uppersurface of the immobilization film is greater than at least one of asurface roughness of an upper surface of the first IDT electrode and asurface roughness of an upper surface of the second IDT electrode. 18.The sensor apparatus according to claim 11, wherein a surface roughnessof a region which is covered with the protective member in an uppersurface of the immobilization film is equal to a surface roughness of anupper surface of the first IDT electrode and a surface roughness of anupper surface of the second IDT electrode.
 19. The sensor apparatusaccording to claim 1, further comprising: a second detecting sectionlocated on the upper surface of the element substrate, the seconddetecting section detecting an object to be detected, using electrodesof different type from those of the detecting section, based ondifferent reaction from reaction of the reaction section.
 20. The sensorapparatus according to claim 1, comprising: a plurality of the elementsubstrates; and a plurality of the detecting sections.